Electromagnetic radiation is known to have many benefits. For example in the area of medical therapies, wavelengths of 680, 730 and/or 880 nanometers have been shown to increase cell growth and speed wound healing (especially when combined with hyperbaric oxygen), and have been used to activate photoactive agents for various cancer treatments. (See Whelan et al., “NASA Light Emitting Diode Medical Applications From Deep Space to Deep Sea,” Space Technology and Applications International Forum—2001, American Institute of Physics, pp. 35-45 (2001).)
In the case of infrared heating, an infrared heating system optimally raises the temperature of a target with the least energy consumption. Such a system may comprise a device that can directly convert its electrical power input to a radiant electromagnetic energy output, with the chosen single or narrow band wavelengths that are aimed at a target, such that the energy comprising the irradiation is partially or fully absorbed by the target and converted to heat. The more efficiently the electrical input is converted to radiant electromagnetic output, the more efficiently the system can perform. The more efficiently the radiant electromagnetic waves are aimed to expose only the desired areas on the target, the more efficiently the system will accomplish its work. The radiation emitting device chosen for use should have an instant “on” and instant “off” characteristic such that when the target is not being irradiated, neither the input nor the output energy is wasted. The more efficiently the exposed target absorbs the radiant electromagnetic energy to directly convert it to heat, the more efficiently the system can function.
In addition, for a particular system or therapy, care must be taken to properly select the output wavelengths such that it matches the absorptive characteristic of the target. The wavelengths required will be different for different targeted applications. Unfortunately, most radiation delivery systems either provide a wide, multichromatic distribution of wavelengths to a target, or a select few wavelengths of monochromatic radiation.
In addition, current products requiring high intensity uniform illumination over the spectral range including ultraviolet (UV) to infrared (IR) are based primarily on mercury arc lamps, which are expensive, inefficient, contain toxic materials dangerous to the environment, short lived, and operated by costly and high voltage ballasts. Xenon and metal halide short arc lamps have also been used, as have tungsten halogen sources. As with mercury arc lamps, both xenon and metal halide lamps also contain toxic materials, expensive power supplies and ballasts and suffer from short lifetimes, requiring frequent replacement, interruptions in progress, and additional costs associated with both the labor for replacement and the lamp itself. A further disadvantage of tungsten halogen based systems is the relatively low output particularly for short blue and UV wavelengths. Additionally, very large voltages are required from power supply ballasts on the order of kilovolts to start the lamps. These high voltages can damage sensitive medical and industrial instrumentation due to the emitted electromagnetic pulse. In addition to these issues with the use of mercury, xenon, and metal halide lamps, recent concern over the use of highly toxic materials has fueled the search for alternatives to the arc lamps and improvements over the low output and poor lifetime of tungsten based lamps. Additionally, the warm up time for mercury, xenon and metal halide lamp systems is relatively long and they cannot be pulsed on and off effectively.
Likewise, quartz infrared heating lamps, which are well known in the art and are used for various process heating operations, will often produce a peak output in the 0.8 to 1 micrometer range. Although the output may peak between 0.8 and 1 micrometers, these lamps have substantial output in a wide continuous set of wavelength bands from the ultraviolet (UV) through the visible and out to about 3.5 micrometers in the middle-infrared. Quartz lamps are “slow on” and “slow off” devices and cannot practically be rapidly pulsed at high frequencies.
In addition, many optical energy applications require high intensity, spatially uniform, light that does not significantly heat the surrounding environment in the near field and/or far field. For example, tungsten filament lamps have a low electrical to optical efficiency and, thus, require large amounts of electrical power to generate high intensity optical energy, which results in large quantities of thermal energy. Furthermore, high power tungsten lamps have a low lamp lifetime, usually operating for about 500 hours. Xenon arc lamps provide optical energy with higher intensity than metal halide lamps, but have a low luminous efficiency and low lamp life time (around 500 hours). Furthermore, traditional light sources such as arc lamps, for example, when used as a light source for a less than spherical illumination region, are optically inefficient.
Accordingly, there is a long-felt need to for radiation devices or apparatus that can provide a desired wavelength or wavelengths of electromagnetic radiation, at a desired radiant power output, in an efficient manner such that the power consumption is both practical and the heat generated to the surrounding environment is minimized.